Conventionally, there has been known a power supply which includes: a plurality of prismatic battery cells; a plurality of separators each of which is sandwiched between two prismatic battery cells arranged adjacent to each other; and a fastening units which holds the prismatic battery cells and the separators. The prismatic battery cell includes: an electrode assembly; an exterior container which houses the electrode assembly; and an insulating film which covers the exterior container (JP-A-2013-033668, for example).
In the power supply, when vibrations are applied to the whole power supply or when respective parts of the power supply are deformed, the prismatic battery cell and the separator which are arranged adjacent to each other move relative to each other so that the prismatic battery cell and the separator rub each other. In this case, when the separator has edges or corners thereof at positions where the separator is brought into contact with an outer surface of an exterior container with an insulating film interposed between the separator and the prismatic battery cell, there may be a case where the edges or the corners rub the insulating film so that a small crack occurs in the insulating film.
In general, the insulating film is made of a resin so that a crack is liable to expand. Accordingly, when a small crack occurs in the insulating film due to rubbing or the like, the crack expands so that dew condensation water or the like is liable to enter the crack whereby insulation property of the exterior container with respect to the outside is deteriorated.